Explain why living organisms need energy and how it is used in cellular processes using evidence from each question and mark scheme.
There are many mitochondria located in the presynaptic knobs of neuromuscular junctions and in the sarcomeres of muscle fibres of striated muscle.
Explain the need for many mitochondria in the presynaptic knobs and in the sarcomeres.
any four from:
1 mitochondria produce ATP ;
presynaptic knob
2 for production of, acetylcholine / ACh ;
3 for, making / moving, vesicles ;
A exocytosis
sarcomere
4 active transport of Ca2+ into, sarcoplasmic reticulum ;
5 detachment of myosin heads / break cross bridge
or
allows myosin head to move back to original position ;
6 AVP ;
e.g. ref. to sodium potassium pump / active transport of Ca2+ out of synaptic knob